Filament stretching apparatus



Jan. 22, 1957 GABLER FILAMEINT STRETCHING APPARATUS 2 She'ets-Sheet 1 Filed Aug. 11 1950 INVENTOR. 01! 527542??? BY MESTERN & r a flrmw'f Jan. 22, 1957 R. GABLER 2,778,058

FIL-AMENT STRETCHING APPARATUS Filed Aug. 11, 1950 2 Sheets-Sheet 2 If f if??? j 1% f zg pazfiy M mm a m FILAIVIENT STRETCHING APPARATUS Rudolf Gabler, Tamins, Switzerland, assiguor to Inventa AG. fuer Forschung und Patentverwertung Luzern, Lucerne, Switzerland Application August 11, 1950, Serial No. 118,802 Claims priority, application Switzerland January '11, 1950 2 Claims. (Cl. 18-8) valuable technological qualities, such as strength, elasticity, color-fastness, dyeability, etc., only after undergoing a stretching process.

While quite a number of synthetic fibers reach optimal quality after a stretch of 2050%, fibers have also be come known of late which require stretching to many times the original length in order to achieve the effects mentioned. To the latter class of fibers belong, inter' alia, the polyamides, polyesters, and polyacrylic nitrile. Many synthetic fibers can be lengthened to the necessary extent cold, while fibers have also become known whose stretching is advantageously carried out hot. However, temperature has no decisive importance for the basic inner and outward phenomena in stretching.

Particularly characteristic symptoms are exhibited in the stretching process of the crystalline synthetic fibers, i. e. fibers whose X-ray diagrams show a high mutual orientation of the molecules.

When stretching these fibers, the uniform length and cross-section change familiar in the plastic, amorphous fiber-forming synthetics over the Whole length of the thread between the stretching organs, does not occur. Instead, the transition from the unstretched to the stretched thread segment takes place suddenly over a short length of thread of only a few tenths of a millimeter. The center of this very short, necklike, transition piece from the unstretched to the stretched portion of an individual thread has been appropriately termed the stretch-point.

It is already known, and was first comprehensively set forth in U. S. Patent No. 2,289,232, that in the case of those polymers forming crystalline fibers which must .be stretched more than 150% of their original length, the necessary uniformity of the stretched thread is only assured when the stretch-point is fixed by mechanical means. Without such precaution, the stretched part of the thread exhibits periodic fluctuations of its physical characteristics which appear not only as irregularities of titre but above all in a variable aflinity for dyestuffs.

The fixation of the stretch-point was hitherto carried .out in accordance with the suggestions of U. 8. Patent No. 2,289,232 with the aid of a brake pin made of mechanically highly resistant material, preferably agate. According to said patent, satisfactory uniformity of dyeing is only to be achieved if the stretch-point is kept within a zone of at most /2". Stretching pins of at most 4-5 mm. diameter around which the thread was wrapped at least one time in order to obtain the necessary braking effect have therefore been used.

A thread rapidly stretched for more than as heretofore described is obviously strained to the limit of its mechanical resistance and subjected to thread and fiber breaks on the stretching pins. This danger is, furthermore, increased by the sharp bending around 360 with a radius of curvature of only 22.5 mm.

It is obvious that the slightest lack of homogeneity in the unstretched thread or yarn, as, for instance, microscopic knots, small bubbles must lead to fiber breaks. Furthermore, extremely unfavorable conditions are brought about 'by the development of heat at the stretching pin caused by inner and outer friction. When stretching multifilarnent silks of crystalline linear polymers and a titre of about 200-300 den., stretch-pin temperatures of l20-150 C. were observed in the vicinity of the stretch zone. As the only materials which possess the necessary mechanical strength for use as break-pins, as for instance agate or ceramics, exhibit poor heat conductivity, an accumulation of heat occurs in the neighborhood of the stretch-zone, which, reacting on the thread contributes to further weakening it and consequently to an increase of the number of fiber breaks.

The object of the present invention is a process for .the production of stretched fiber-formed material of synthetic linear polymers which avoids the disadvantages mentioned above. According to the invention the fixation of the stretch-point takes place at a braking device having .a multiple subdivided surface. The separation of the stretching process into several partial processes, separated in space and closely following each other in point of time not only makes possible a more lenient thread path with large radius of curvature, but their is now also sufficient space to arrange a strong aggregate which conducts off or cools the heat of stretching, as one is now no longer held to the maximum stretch-zone of /2 according to the U. S. patent cited.

-In the accompanying drawing, Fig. 1 and Fig. 2 show diagrammatically perspective views of two embodiments of devices adapted to carry out the present invention.

Fig. 3 shows schematically a complete installation for stretching threads according to the present invention.

The stretching of the thread 1 takes place at the surface of several, as for instance 6 to 10 pins 2 made of a mechanically very resistant material, as for instance agate, vitrified corundum, hard porcelain, quartz, glass, silver steel, tungsten.

The insert pins 2 (Fig. 1) on which the thread is sub- .jected to braking action and stretching may be all of the .same diameter, or of different diameter, as shown in Fig. 2 (2a).

The cross-section of the pins is preferably circular but may also be elliptical.

A massive cylinder of material of good heat conductivity, as for example, silver, copper, brass, bronze, aluminum, etc. serves as holder 3 for the pins.

The holder can be provided with supplementary equipment adapted to regulate temperature in the stretching process, if the process is to be carried out at raised or lower temperature, which may be necessary, for instance if the heat conductivity of the metal'of the holder is not sufficient to deduct the stretching temperature of the thread.

As shown in Fig. 2, the braking device comprises for .this purpose a hollow holder 3a provided with a tubing 4, through which a temperature regulating liquid, for instance cooling water, will be conducted in the interior of said braking device, and with a tubing 5 through which said liquid leaves said hollow holder.

Furthermore, the braking device can be provided with a mechanical drive, which, during the stretching process, imparts to it a uniform rotation in the sense of the direcbe circulated in said braking device.

3 tion of the motion of the thread or opposite thereto. In this manner, the braking etfect of the stretching organ can be increased or diminished.

Fig. 3 shows such a rotatably arranged stretching device. In this particular arrangement the holder 3 of the stretching pins 2 is mounted in a ball-bearing 11. On the rear end of the stretching pin holder a gear 12 is mounted. The stretching device can be rotated by means of a second gear and a motor-driven shaft 13. Although Fig. 3 illustrates merely one of many possible arrangements according to the invention, the illustrated modification is described in detail.

On the holder 17 a bobbin 6 containing unstretched thread is arranged. The thread 1 is guided over a braking member 7 made of china or stainless steel and imparting to the thread a slight pre-tension of less than .2

gram per denier. The thread is further guided over a changing thread guide 8 and runs on the rubber coated roller 9, which is in engagement with a chromium-plated steel roller 10. After encircling partially both rollers, the thread reaches the braking device which consists of a hollow holder 3 and a certain number (six to ten) of stretching pins 2.

The hollow holder 3 is provided at its open end with a stuffing box 19. By means of feeding tube 20 entering through said stuffing box in the hollow holder, and a discharge tube 21 which goes out from the hollow holder through said stufiing box, a cooling liquid may Subsequently, the thread reaches a pulling device comprising a roller 18 and a spacing roller 19, the thread being wound three to four times around this device. The thread eventually reaches through a thread-guiding eyelet the bobbin 15 driven by a spindle 16.

The pins may be revolved in the holder so that worn spots may easily be removed from the path of the running thread. The stretching device thus has, as compared with the breakable agate pins employed hitherto, practically unlimited durability.

If one designates the pin on which the unstretched thread, coming from a usual tension device, as for instance a tension aggregate consisting of delivery cylinder and pressure roller, is fed as the n pin, the pin next in the direction of movement of the thread as the n+1 and the one to the rear as the 11-1, it is to be noted that when the thread is wrapped once around the brake organ, the stretch point should be located at the 12- 1 or n-2 As the stretched thread, under full stretching tension still runs over one or two further pins, possibly unstretched portions which have slipped through are caught here and the titre and structure of the thread finally leaving at the n pin is made even more uniform.

When stretching heavy thread (over 300 denier), it can happen that the stretching action is not quite completed on the n1 pin nor on the n pin. In this case, the thread leaving the stretching device will show irregularities of gage and stretching. It would be possible to Wind such heavy thread twice around the stretching device. This would mean doubling of the braking friction and this would be excessive in most cases and would lead to breakage of the thread.

However, the rotatable arrangement of the braking device makes possible the individual adjustment of the braking action to the prevailing gage of the thread to be stretched, as a rotation opposite to the thread movement shifts the point of ultimate stretching backwards and a rotation in unison with the thread movement shifts the stretching point forward. The latter is recommended if very fine threads (gage less than 20 denier) are stretched. In the manner described it is always possible to shift the stretching point in such a manner that the stretching is terminated at the latest on the n1 pin.

The inventor has found that despite the extension of the extension zone according to this invention to far more than /2", namely for instance to 1- the stretched threads exhibit a considerably improved uniformity of titre and mechanical qualities as compared with the produce of stretching with the simple pin.

Thus, for instance, a 12-thread yarn of 30 denier of poly-e-caprolactam which was stretched by means of a 6 fold divided braking device of 18 mm. diameter exhibited a mean deviation of the titre from the averagevalue of 0.3 denier, determined on short pieces of threadof 3 cm. length.

The increased uniformity of the threads stretched ac cording to the invention is shown not only by the results of physical tests, but also in the chemical affinity to dyestuffs which adhere to the stretched fibers in completely uniform color shades and intensities.

It was furthermore found that with brake-organs as invented of more than /2" diameter the number of fiber breaks recedes, which is due to the more gentle threadpath at the brake-organ and the better heat dissipation. In the case of a 60-thread yarn of 265 denier, of poly-@- caprolactam, the fiber-break figure could be reduced from 8.4 to 5.5 breaks per 100 km. by means of an 8-fold subdivided stretching organ of 20 mm. diameter.

Example 1 A 12-thread yarn of 105 denier of poly-e-caprolactam was passed through a feed device consisting of feed cylinder and rubber coated pressure roller, at a speed of m./min. en the thread was laid once around a brake-organ, as per Fig. l, of 18 mm. diameter and drawn off by means of a chrome-plated stretching roller with a speed of 175 m./minute. The 20 denier stretched silk exhibited in 3 cm. sections an irregularity of titre of 21.0%, of strength of :2.8%, and of elongation of Example 2 A 24-thread yarn of 220 denier of poly-hexamethylene adipate was passed through a feed device consisting of feed cylinder and rubber coated pressure roller at a speed of 80 m./min. Then the thread was wrapped once around a brake-organ as per Fig. 2 of 22 mm. diameter and drawn otf by means of a chromeplated stretching roller at a speed of 300 m./minute. The stretched 60 denier silk exhibited an irregularity of titre of -O.S%, of strength of i3.1% and of elongation of i4.5%.

I claim:

l. A device for stretching filiform materials of synthetic linear polymers a multiple of their original length, comprising: two systems of rollers between which the filiform material is stretched, a braking device disposed between said rollers and around which said filiform material is wound at least once, said braking device consisting of 3. generally cylindrically shaped holder and a plurality of fixed braking pins recessed in the surface of the holder, means for cooling the holder and the pins to dissipate the heat generated by stretching the filiform material at said braking device, means for rotating said holder axially to adjust the braking efiect.

2. The apparatus of claim wherein the braking pins are agate pins of circular cross section. 

